As is well known in the manufacture of cement, there results as waste a kiln dust which heretofore had no economically viable utility, but presented considerable disposal problems and cost.
While there have in the past been proposed certain uses for waste cement kiln dust, such as a soil liming agent in agriculture, a soil stabilizer for road beds and the like, and for reuse in cement manufacture, such proposals have not proved acceptable. For example, as a soil liming agent such waste material is damaging to plant leaves by its high alkalinity and difficult to control because of its fine particle size. In road work and similar construction solubility of the high alkaline waste material is now considered a pollution hazard and is therefore undesirable. Also as an ingredient in the manufacture of cement via recycling, the waste kiln dust has been found to degrade the quality of the resultant cement product.
That neither these nor other acceptable uses have been found for waste cement kiln dust is evidenced by the current building of expensive storage containers, the expensive collecting, transporting, and other handling of the kiln dust, as well as the continuing cost of storage space, and the like. By way of example, a single medium size cement plant generates approximately 100 tons of waste dust per day, or about 30,000 tons per year, so that the continuing and increasing size of this problem may be appreciated.
Applicant is aware of the below listed prior patents in this area of endeavor:
______________________________________ PATENTEE U.S. Pat. No. ______________________________________ Ponzer 2,329,940 McCants 2,605,236 Palonen et al. 2,871,133 Patzias 2,991,154 Singleton et al. 3,925,534 ______________________________________
Both Ponzer and Palonen et al. propose recycling the kiln dust, Ponzer in a slurry and Palonen by agglomeration under high heat. Singleton et al. also suggests recycling by a slurry, McCants teaches the production of an adsorbent paste, while Patzias teaches the recovery of potassium sulphate.